On the use of distributed synchronization in 5G device-to-device networks

Time synchronization is a key aspect of device-to-device (D2D) schemes, particularly in decentralized networks where no reference time is available. Distributed phase-locked loops (DPLL) is a synchronization algorithm well suited for decentralized situations. In this work, we study DPLL in the context of 5G networks, where we include in our analysis several practical aspects of D2D communication, such as propagation delays, multipath propagation, and the use of single-carrier frequency division multiple access (SC-FDMA). We propose practical methods to compensate for their effects, and introduce new performance metrics to evaluate the merits of the synchronization algorithm. Through simulations at the physical layer, which capture the effects of analog-digital conversions, we demonstrate that time synchronization in a decentralized setting is possible under the constraints specified by the 3GPP for D2D applications.